Defect-modulated oxygen adsorption and Z-scheme charge transfer for highly selective H2O2 photosynthesis in pure water.

Abstract

Solar-driven H2O2 production provides an eco-friendly and scalable alternative to conventional anthraquinone processes. However, its efficiency has been limited by the inefficient charge separation and poor selectivity for the two-electron oxygen reduction reaction (2e- ORR). Here we report a Z-scheme heterojunction photocatalyst constructed by in-situ growth of sulfur-deficient ZnIn2S4 nanosheets onto UiO-66-NH2 (a zirconium-based metal-organic framework). This heterojunction promotes efficient charge separation while retaining strong redox capability, and sulfur vacancies regulate O2 adsorption into a configuration that suppresses O-O bond cleavage and favors 2e- ORR. As a result, the composite achieves a high H2O2 production rate of 3200 μmol g-1 h-1 with 94.3% selectivity in pure water under ambient air and visible light. A continuous-flow prototype exhibits stable performance for over 200 h, and the generated H2O2 solution enables direct bacteria disinfection. Spectroscopic and theoretical analyses reveal the critical role of sulfur vacancies in optimizing O2 activation. Our findings highlight a synergistic strategy of tuning charge dynamics and O2 adsorption configurations for designing next-generation systems for sustainable H2O2 production and water disinfection.